The
cyclol hypothesis was the first
structural model of a
folded,
globular protein. It was developed by
Dorothy Wrinch in the late 1930's, and was based on three assumptions. Firstly, the hypothesis assumes that two
peptide groups can be
crosslinked by a
cyclol reaction; these crosslinks are
covalent analogs of
non-covalent hydrogen bonds between peptide groups. These reactions have been observed in the
ergopeptides and other compounds. Secondly, it assumes that, under some conditions, amino acids will naturally make the maximum possible number of cyclol crosslinks, resulting in
cyclol molecules and
cyclol fabrics. Finally, the hypothesis assumes that globular proteins have a
tertiary structure corresponding to
Platonic solids and
semiregular polyhedra formed of cyclol fabrics with no free edges.
Although incorrect as a model for the structure of globular proteins, several elements of the cyclol model were later verified, such as the cyclol reaction itself and the hypothesis that hydrophobic interactions are chiefly responsible for protein folding. The cyclol hypothesis stimulated many scientists to research questions in protein structure and chemistry, and was a precursor of the more accurate models hypothesized for the DNA double helix and protein secondary structure. The proposal and testing of the cyclol model also provides an excellent illustration of empirical falsifiability acting as part of the scientific method.
Vitrification is a process of converting a material into a glass-like amorphous solid which is free of any crystalline structure, either by the quick removal or addition of heat, or by mixing with an additive. Vitrification is a proven technique in the disposal and long-term storage of nuclear waste or other hazardous wastes. Waste is mixed with glass-forming chemicals to form molten glass that then solidifies, immobilizing the waste. The final waste form resembles obsidian and is a non-leaching, durable material that effectively traps the waste inside. The above image demonstrates this process.
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